The present invention relates generally to a mammography apparatus and more particularly to an improved upper and lower compression plate arrangement for applying compression to the augmented breast during mammographic examination.
Mammography is an X-ray examination technique used to detect and discover anomolies of the female breast, including lumps, distortions or calcification in the tissue. It is general practice to apply vigorous compression to the breast to improve the quality, contrast and sharpness of the resulting X-ray picture. Various devices can be found in the prior art for applying pressure to the breast during such examinations, however, none address the problem of mammography examination of prosthetically augmented breasts. For example, U.S. Pat. No. 3,824,397 shows a device in which pressure is applied to a plastic sheet which is placed on the breast.
U.S. Pat. No. 4,090,084 relates to a mammography apparatus having a pressure plate which is mounted so that the pressure can be applied uniformly throughout the breast area. To enable such uniform pressure to be obtained, the pressure plate is connected at its opposite ends to a slide which is mounted on tracks on the cone of the X-ray machine.
U.S. Pat. No. 4,259,585 describes a device in which a compression plate is mounted parallel to the support plate and is adjustable relative to the support plate to adjust the spacing therebetween. The compression plate is provided with a cut-out area. At the margin of the cut-out section, marking is provided which is reproducible on the X-ray film for locating a specific point in the cut-out section.
U.S. Pat. No. 4,122,350 suggests the use of a collimating device provided to restrict the X-rays. The collimator is designed to fit closely over the breast, the collimator being adjustable.
While various mammography compression devices are suggested in the prior art, they do not provide appropriate compression of the breast tissue in patients who have undergone breast augmentation procedures involving the placement of prosthetic implants behind the breast tissue.
A particular problem occurs with patients who have had breast augmentations with implants. It is estimated that over a million women nave undergone augmentation mammaplasty in the United States. The breast implant generally consists of a silicon gel or saline solution encapsulated within a flexible envelope. The implant is effectively radiographically opaque.
With conventional dedicated mammography systems the lower support table is generally fixed and the upper plate is movable to apply compression to the breast. As the movable compression plate is lowered to apply compression to the breast, the prosthesis also becomes entrapped along with the breast tissue, totally or partially obscuring portions of the breast tissue and thus degrading or interfering with the resulting X-ray photograph. For a discussion of the effects of breast prosthesis on the screening technique see "Mammograph and Breast Implants" in Plastic and Reconstructive Surgery, July, 1988, Vol. 82, No. 1, Pages 1-7.
Accordingly, in view of the foregoing, it is a primary object of the present invention to provide an improved mammography compression apparatus which facilitates the taking of satisfactory mammographs in patients who have undergone augmentation mammaplasty.
Another object of the present invention is to provide mating upper and lower compression plates for X-ray mammography, which plates are cooperatively contoured to avoid trapping the prosthetic envelope during the compression of the breast tissue. The compression plate may be provided as original equipment or may be appropriately adapted to an existing X-ray apparatus.
Another object of the present invention is to provide compression plates for a mammography X-ray system having relieved areas which allow the plates to pass along the prosthesis without trapping the prosthesis therebetween.